Abstract

The fossil turtles from the Upper Cretaceous Fruitland and Kirtland formations (late Campanian; Kirtlandian) have been known for more than 100 years. We re-assess and revise these Late Cretaceous testudine taxa from the San Juan Basin, New Mexico, USA, and discuss their biostratigraphic distribution. We recognize the following valid taxa as present: the bothremydid Chedighaiihutchisoni; the pleurosternid Compsemys sp.; the baenodds Denazinemysnodosa and Scabremys gen. nov., established for the distinct species S. ornata, previously included in Denazinemys; and Boremysgrandis, though it is a rare taxon. The non-baenodd baenid Neurankylusbaueri is recognized as a valid species. Two additional non-baenodd baenid taxa, Thescelushemispherica and T. rapiens, are retained as distinct species and are not considered synonymous with T. insiliens. We also recognize a small indeterminate kinosternoid similar to that reported from the Campanian of Mexico. The two adocids Adocusbossi and A. kirtlandius are retained as distinct species. The nanhsiungchelyid Basilemysgaffneyi sp. nov. is established, whereas Basilemys nobilis is considered a nomen dubium because it lacks the diagnostic features that would allow referral to any known valid species. We recognize three trionychids: Aspideretoidesausterus and A. robustus (new combination), and an unnamed plastominine. We synomize Aspideretoides fontanus and A. vorax with A. austerus. Aspideretoides ovatus is considered a subadult of A. robustus. The unnamed plastominine may represent a new genus and species. Turtles of the Fruitland-Kirtland formations resemble other late Campanian turtle assemblages from western North America, and are part of the characteristic vertebrate fauna of the Kirtlandian land-vertebrate age. The upper Fruitland and lower Kirtland formations (Hunter Wash local fauna) have greater turtle taxonomic diversity than the upper Kirtland Formation (Willow Wash local fauna). This apparent decrease in taxonomic diversity is interpreted as being real and reflects a shift in depositional (channel) environments to a more terrestrial one, a pattern which is seen in other North American Late Cretaceous settings.

Keywords

Fruitland Formation
Kirkland Formation
Late Cretaceous Late Campanian San Juan Basin
New Mexico

Notes

Acknowledgments

This study was made possible by the assistance and help of a number of individuals. For access to collections we thank Eugene S. Gaffney, Mark Norell, and Carl Mehling, (all American Museum of Natural History); John Bolt and William Simpson (both Field Museum of Natural History); Larry Martin and Desui Miao (both University of Kansas); Solwieg Stuenes (Paleontologiska Museet, University of Uppsala); and Michael Brett Surman (United States National Museum, Smithsonian). For discussions and verification of specimen identities we thank Don Brinkman (Royal Tyrrell Museum of Palaeontology); Walter Joyce (University of Tübingen), and Tyler Lyson (Yale University). For help in the field we thank John Burris (San Juan Community College), Mike Burns (University of Alberta), Denver Fowler (Montana State University), Kesler Randall (San Diego Natural History Museum), and Justin A. Spielmann (New Mexico Museum of Natural History and Science). Additional field assistance provided by independent individuals include Arjan Boere, James Hartley, James Nikas, Jim Murphy and Fred Widmann. Kevin Seymour (Royal Ontario Museum) kindly provided the information for ROM 864, and we thank him for these data. Donald Brinkman, Derek W. Larson (University of Toronto), and J. Howard Hutchison reviewed the manuscript, and we thank them for their valuable comments and suggestions. Finally, we thank Pat Hester and Sherrie Landon (Bureau of Land Management, Albuquerque and Farmington offices) for providing the necessary Paleontological Resource Permits for collecting specimens housed in the collections of the NMMNH and the SMP, and for their continuing support of our fieldwork.

Appendix

List of all known previously referred, and newly referred, turtle specimens from the Fruitland and Kirtland formations, as of 2010. Order is alphabetic by (1) family/higher taxonomic category, (2) genus, (3) species, and (4) institution.

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